The present invention relates to an airbag apparatus used for vehicles.
Conventionally, airbag apparatuses that are located in the center of a steering wheel are known. Such an airbag apparatus includes an airbag and an inflator for supplying inflating gas to the airbag. The inflator is provided between spokes of the steering wheel and below the pad of the steering wheel. The pad includes a thin portion that corresponds to the outer shape of the airbag apparatus. When an impact the magnitude of which is equal to or greater than a predetermined value is applied to the vehicle, the inflator supplies gas to the airbag. Accordingly, the airbag breaks the pad at the thin portion and is deployed at the outside of the steering wheel. This reduces the influence of the impact of collision to the occupant.
In an airbag apparatus described above, the pad is broken along the thin portion, and an opening, or a port, is formed during an initial stage of the airbag deployment. Therefore, some of the energy for deploying the airbag is used for breaking the thin portion. This extends the time required for the airbag deployment to be completed.
As another type of a prior art airbag apparatus, Japanese Laid-Open Patent Publication No. 2001-206176 discloses an airbag apparatus 300 shown in FIGS. 24 to 26. As shown in FIG. 24, a first airbag module is provided in a door 210. The first airbag module includes a first inflator 288, a first airbag 282, and a contacting plate 286. When a collision of the vehicle is predicted based on detection by a pre-crash sensor (not shown), the first inflator 288 is activated to deploy the first airbag 282 toward the interior of a vehicle passenger compartment S as shown in FIG. 25. The deployment moves the contacting plate 286 toward the interior of the passenger compartment S and pushes an occupant toward the interior of the passenger compartment S.
A second airbag module is supported on the first airbag 282. The second airbag module includes a second inflator 290 and a second airbag 284. When the first airbag 282 is deployed, the second airbag module is pushed into the passenger compartment S. Thereafter, when a collision sensor (not shown) detects a collision of the vehicle, the second inflator 290 is activated and deploys the second airbag 284 between the occupant and the door 210 as shown in FIG. 26. This reduces the influence of the impact of the collision to the occupant.
The second airbag 284 is projected into the passenger compartment S in an undeployed state when the first airbag 282 is deployed. However, after being projected, the second airbag 284 is inflated on the unstable first airbag 282. Therefore, the second airbag 284, which chiefly protects the occupant, can be inflated at a position that is not suitable for protection. Even if the second airbag 284 is deployed at a position corresponding to the occupant, the second airbag 284 can be displaced due to contact with the occupant and therefore cannot effectively absorb the impact. Accordingly, the second airbag 284 cannot effectively protect the occupant under certain circumstances.